A “powder”, as used herein, is a fluffy material which is composed of fine, loose particles. “Unit weight” is weight per volume and is generally expressed as pounds per cubic foot or grams per cubic centimeter. The unit weight will vary according to the specific material. For example, non-compacted calcined kaolin may have a unit weight of 10 to 15 pounds per cubic foot; while non-compacted air floated kaolin may have a unit weight of 18 to 30 pounds per cubic foot.
Fluffy, low unit weight powders can be difficult to handle with conventional bulk handling systems. These products are typically shipped dry in bags via truck, rail box car or container, or in bulk rail cars or bulk highway trucks. The volume of the container, rail car or truck is often filled before the allowed weight is reached, which results in higher shipping costs.
Efforts have been made to improve the unit weight, to reduce dusting, and to improve flow characteristics, of fluffy powders by compaction, especially calcined kaolin, with varying degrees of success. Low unit weight, fluffy powders, however, generally cannot be compacted in traditional compacting equipment without additives due to difficulties in feeding the powder into the compaction zone of the equipment.